I have no direct, firm "answer" for you. You were not really asking for one. You asked for "thoughts."
My thought is to steer you to the book
Being Mortal, by Dr Atul Gawande, for sage counsel and guidance on what confronts your dad, and eventually all of us. This easy-to-read book also happened to be the Jan/Feb selection for the HW/PC Book Club. (
LINK to Book Club discussion)
This book is "
....a valuable book which I would recommend for anyone who has ever known someone who is going to age or die, or is going to age or die themselves." It, too, will not give you answers, but it will help bring clarity to your question of longevity and quality of life. Whipple procedure is also amongst the cases discussed in the book.
Available in many formats here at Amazon:
/www.amazon.com/Being-Mortal-Medicine-What-Matters/dp/0805095152/ref=asap_bc?ie=UTF8Post Edited (JackH) : 5/19/2017 8:12:04 AM (GMT-6)